Conventionally, a thermal fixing device has been proposed for an electro-photographic type image forming device. The fixing device includes a fixing belt, a heater disposed in an internal space of the fixing belt, a nip plate, a pressure roller, and a reflection plate that reflect radiant heat from the heater to the nip plate. A nip region is defined between the nip plate and the pressure roller through the fixing belt. A temperature sensor is provided to detect a temperature in order to control the heater for controlling a fixing temperature.
In another thermal fixing device having a construction similar to that of the above-described fixing device, a holding member (stay) is provided for supporting the nip plate.